Capacitors are important components of many electronic devices, and in particular mixed-signal circuits that process both analog and digital circuitry. Capacitors can be manufactured separate from and then coupled to integrated circuits (ICs) as external capacitors. Capacitors can also be integrated into the ICs. Compared to external capacitors, integrated capacitors consume less space, have lower profiles, and generally are easier to include in low-profile electronic devices such as mobile phones.
A conventional capacitor structure is a planar metal-insulator-metal (MIM) structure, and one such structure is shown in FIG. 1. FIG. 1 is a cross-sectional view of a metal-insulator-metal (MIM) capacitor according to the prior art. A capacitor 100 includes an insulator layer 104 surrounded by metal layers 102 and 106. A capacitance of a MIM structure is related to the lateral area (L*W) of the MIM capacitor and the thickness (T) of the insulator layer 104. The capacitance provided by conventional planar MIM capacitors, such as that of FIG. 1, limits the density of circuitry on a substrate that includes integrated capacitors.
Shortcomings mentioned here are only representative and are included simply to highlight that a need exists for improved electrical components, particularly for capacitors employed in consumer-level devices, such as mobile phones. Embodiments described herein address certain shortcomings but not necessarily each and every one described here or known in the art.